1. Functions of Somatosensory System

• Haptic Sensors
  • Provide close-range sensory information important to plan and execute motor action

Basic Functions of the Somatosensory System

<aside> 💡 Haptic - 触觉的 Nociception - 疼痛感受 Proprioception - 自体感受

</aside>

• To control posture with the proprioceptive system and to interact with objects with appropriate forces with skin mechanoreceptors
• Information is integrated with information from other sensory systems to produce behaviour
  • Monitor forces acting inside and outside of the body
  • Identify shapes and texture of object
  • Build up a sense of self (Proprioception)
• The Somatosensory System is divided into 2 subsystems:
  • Mechanosensation
  • Nociception (Pain and Temperature Reception)

Classification of Sensory Fibres in Peripheral Nerves

Nociception - Nociceptors

• Uses Nociceptors to turn physical energy into neural signals
  • Nociceptors located in the skin next to several other Mechanoreceptors
  • Information sent form Nociceptor Afferent Fibres to Dorsal Horn in Spinal Cord and then to Brain
• Pain information is encoded in a somatotopic map which facilitates the integration of signals from both Mechanoreceptors and Nociceptors

Mechanosensation - Mechanoreceptors

Location and Morphology

• Cutaneous and Subcutaneous Receptors mediate sensation of touch, texture and pain
  • Superficial Layers - Epidermis: Cutaneous Receptor
  • Deeper Layer - Dermis: Subcutaneous Receptor
• For Mechanoreceptors:
  • Cutaneous:
    • Meissner Corpuscle
    • Merkel Disk Receptor
  • Subcutaneous:
    • Pacinian Corpuscle
    • Ruffini Ending
• Except for some bare nerve endings, most of the Mechanoreceptors are innervated by myelinated axons

Transmission to CNS

• Somatosensory afferents conveys information about the entire body through a series of Dorsal Root Ganglia distributed along the Spinal Cord
• Information from Cutaneous Mechanoreceptors is sent to the Spinal Cord
  • Soma of these Afferent Fibres are located in the Dorsal Root Ganglia adjacent to the Spinal Cord
  • Axons enter the Spinal Cord through Dorsal Roots